In irrigated perimeters, upward capillary fluxes from shallow water tables increase salinization hazards. When natural drainage is insufficient, artificial drainage helps controling these hazards by evacuating a fraction of the depth of irrigation water applied in order to leach the salts brought by irrigation water. In such conditions, drainage functionning is influenced by upward capillary fluxes which supplying evapotranspiration and contributing to the watertable drawdown. The classical design methods, inherited from temperate regions, do not take drainage and evapotranspiration interactions explicitely into account. The aim of this thesis is to provide a better understanding of upward capillary fluxes and hydraulic drainage functionning interactions to improve drainage design. Evaporation from watertable mechanisms are studied in a lysimeter tank. It is demonstrated that daily variations of the evaporative demand are responsible for significant variations of upward fluxes from the water table; the use of the drainable porosity concept is also shown not to be easily applicable in such situation. The saturated zone functionning is also simulated by the Boussinesq's equation spacially integrated ; the influence of a boundary condition (recharge or evaporation) on discharges and watertable levels at drain midspacing is studied; the great variability of the water table's shape and its consequences on the drain discharges is discussed. A new design approach is proposed which is based on the drainage schemes restitution computation and on the verification of the leaching fraction criteria.
